I think, for the sake of roleplay, Mason needs some kind of innate awareness of mirrors. For example, if he is confronted with a locked door, he would be able to sense whether there is a mirror in the locked room. When he's in the mirror world, the mirror he is teleporting to gives off an energy that draws him toward it. 

Without these passive abilities, there is going to be a lot of RP time spent wandering aimlessly in the mirror world for a mirror that might not even exist. However, I am aware you felt my powerset was already OP, so I thought I would run this by you first, [@Mr Allen J] and [@UrbanEvolution].